【摘要】 印度尼西亚穿越流（Indonesian Throughflow,简称ITF）控制着印度洋和太平洋间的水体与热量交换,显著影响着现代印度太平洋地区的气候环境,且在过去的区域水文条件演变中也起了至关重要的作用。目前,有关ITF在轨道-亚轨道时间尺度上的研究多限于末次冰期以来,对其在多个冰期旋回中的演变缺乏认识。本文利用位于ITF帝汶海出口处的IODP 363航次U1482钻孔（15°3.32’S,120°26.10’E;水深1446m）,通过浮游有孔虫Trilobatus sacculifer壳体的氧同位素和Mg/Ca分析,建立了U1482钻孔上部42.48 m的年龄框架,重建了620 ka以来帝汶海西南部表层海水温度（Sea Surface Temperature,简称SST）和剩余氧同位素(δ¹⁸O_sw-iv)的变化。结合西太平洋暖池区和帝汶海的其他岩芯记录,探讨了近6次冰期旋回中ITF结构和强度变化导致的区域盐度演变特征及机制。结果显示,620 ka以来帝汶海西南部δ¹⁸O_sw-iv呈现出冰期低、间冰期高的特征,且其变化具有显著的岁差（23 ka）和斜率（40 ka）周期。分析表明,岁差驱动下热带辐合带（Intertropical Convergence Zone,简称ITCZ）南北位移所致的盛行风向变换以及冰期旋回中海平面升降导致的ITF通道连通性的改变是区域盐度周期性演变的主导因素,同时,地球轨道斜率驱动下南半球经向温度梯度的周期性变化也可能影响了ITF低盐水体向南半球高纬海区的输运。更多还原

【Abstract】 The Indonesia Throughflow（ITF）,which regulates the water and heat exchange between the Pacific Ocean and Indian Ocean,has significant influence on the recent climate and environments in the Indo-Pacific region.Also,it exerted a crucial role in the evolution of regional hydrological conditions during the past times.However,most of the existing studies on the changes of the ITF in geological history are limited to the last glacial period with insufficient knowledge on its evolution over multiple glacial cycles.International Ocean Discovery Program（IODP） Site U1482（Expedition 363）,535.86 m core composite depth below seafloor（CCSF） in length,is located on the Scott Plateau off the northwest Australian margin at 15°03.32′S,120°26.10′E and 1466 m below sea level.The site is within the prominent hydrographic front between subtropical water mass in the Eastern Indian Ocean carried northward by the West Australian Current and the tropical waters from the ITF,which makes it suitable for reconstructing the variations of the ITF outflow into the Indian Ocean in the past glacial-interglacial cycles.In this work,the upper 42.48 m CCSF of Site U1482,with lithology dominated by foraminifera-rich nannofossil ooze,was used to reconstruct the seawater residual oxygen isotope(δ¹⁸O_sw-iv) based on δ¹⁸O and Mg/Ca analyses of planktonic foraminifera Trilobatus sacculifer,and thus to investigate the variations in the sea surface salinity related to the evolution of the ITF over the past 620 ka.Totally,226 samples,subsampled at intervals of20 cm,were analyzed,providing an average temporal resolution of 3 ka.In more details,the age model was determined by 14 age tie points,derived from correlating the present δ¹⁸O curve with the standard LR04 stack as well as the last appearance of Globigerinoides ruber（pink） with a well-known age（120 ka） in the Indian Ocean.The temperature-corrected planktonic foraminiferal δ¹⁸O record constrains global changes in ice volume,yielding a δ¹⁸O_sw-iv record that primarily reflects regional salinity.Our results indicate that the variability of δ¹⁸O_sw-ivshow significant precession（23 ka） and obliquity（40 ka） cycles with a weaker 79 ka-period over the past 620 ka,implying the direct responses of regional hydrological conditions to orbital changes.We suggest that the periodic fluctuations of prevailing wind and the meridional migrations of the Intertropical Convergence Zone driven by precession could influence the structure and strength of the ITF,and then the salinity in the southwest of the Timor Sea.And,the 79-ka component for the δ¹⁸O_sw-iv record coincides with the periodic onset of deglaciation,indicating the considerable role of the global sea level fluctuations in the regional hydrology during the glacial cycle that determined the connectivity of the ITF channels among the Indonesian archipelagos.In addition,the variations in the meridional temperature gradient in the southern hemisphere driven by the obliquity of the Earth’s orbit could also affect the southward transport of the ITF fresh water to the high-latitude areas,resulting in periodic revolutions of the regional salinity with a prominent 40-ka period during the last six glacial cycles.更多还原